Structure and solubility of pea seed-derived ingredients produced by air classification: Relevance of the seed milling process and endogenous lipid accumulation

With the increase in the use of plant ingredients in food and the growing demand for pulse protein ingredients, dry fractionation is a sustainable method for producing high-quality protein fractions from pulses. The objective of this work was to assess the morphology of pea fractions obtained by dry fractionation, and their detailed composition with a focus on non-protein components, especially lipids. Pea seeds from a single cultivar were first dehulled, then milled via either stirred ball milling or impact milling, which affected the microstructure of the flours. For instance, scanning electron microscopy revealed that starch granules looked damaged after stirred ball milling, whereas impact milling led to flours with smooth starch granules. Air classification led to a protein-rich fraction (concentrate) with at least 46 g protein /100 g dry matter (d.m.) and to a protein-poor fraction with maximum 18 g protein /100 g (d.m.). The lipids endogenously present in pea seeds (around 3 g/100 g (d.m.) in the starting flour) accumulated in the protein-rich fractions (> 5 g/100 g (d.m.), at the expense of the protein-poor fractions where the lipid content decreased compared to the flour. The same trend was obtained for the ash content. Finally, protein solubility in the flours and protein-rich fractions was investigated in aqueous suspensions at neutral pH, and could be improved by applying a high-pressure homogenization treatment. The microstructure of the suspensions (non-treated, or treated with high-pressure homogenization) was also characterized by confocal laser scanning microscopy. These outcomes expand the current knowledge of dry-fractionated pulse protein concentrates, which is particularly important when targeting their rational use for food applications.